Performance Low when Heater is on
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"Legendary"
Joined: Jul 2007
Posts: 657
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From: Seattle, WA
Performance Low when Heater is on
Hey Guys,
I've noticed that on some days my FD will hesitate if I'm trying to accelerate at lower rpms usually between 2-3 grand. Anything above 3 grand and it runs like a champ, so its either on or off the throttle. This morning I've figured it out that if my heat is turned up high it will do this but as soon as I turn the heat off or to LOW, my fd will drive fine without any kind of hesitation. I tested this at least half a dozen times.
Some things that may or may not be irrelevant: No check engine light is on. All hoses were recently replaced. I did get a check engine light a while back regarding feedback relay on the O2 sensor but it went away and hasn't come back since. No problems with idle.
If someone could 1) explain any or all connections between the heat system and the engine or where I could find this info and 2) point me in the direction I should be looking at, I would really appreciate it. I am almost certain its some kind of sensor or vacuum going awry.
Thanks!
I found this on turborx7.com but my car does this whether or not its cold or warm.
Hesitation at 3000 RPM when cold: No known cure.
I think it is caused by the double throttle control. Its purpose is to
prevent the engine from getting an overly lean fuel/air mix when you
first start to accelerate. Now the way this system works is that when
the engine is cold, (coolant below 175 degrees or so) the ECU opens the
double throttle control solenoid, which supplies vacuum to the double
throttle control actuator. This vacuum overcomes the spring tension
that normally holds the double throttle butterfly open, and it closes.
Now, think about what happens when you accelerate.... the engine pulls
less vacuum, and starts to go towards positive manifold pressure as you
build boost. With the vacuum going away, the plate returns to its
open (normal when engine warm) position. This helps explain why the car
doesn't hesitate when accelerating hard, and does when accelerating slowly.
The decision by the ECU to operate the double throttle control system is
affected by coolant temperature, and the current "map" that the ECU is
using. The Double Throttle control only happens during starting, cold
engine warm-up, and COLD engine with LIGHT LOAD operation. This map is
also affected by the 20k mile switch, which is why many people say that
the car never hesitated at 3000 RPM when it was new. The 20k mile switch
does the same thing that the EL switch does.... it adds base RPM to the
motor... which affects the ECU's decision as to what "map" it is currently
operating in.
This is just my personal theory, and may be wrong.
I've noticed that on some days my FD will hesitate if I'm trying to accelerate at lower rpms usually between 2-3 grand. Anything above 3 grand and it runs like a champ, so its either on or off the throttle. This morning I've figured it out that if my heat is turned up high it will do this but as soon as I turn the heat off or to LOW, my fd will drive fine without any kind of hesitation. I tested this at least half a dozen times.
Some things that may or may not be irrelevant: No check engine light is on. All hoses were recently replaced. I did get a check engine light a while back regarding feedback relay on the O2 sensor but it went away and hasn't come back since. No problems with idle.
If someone could 1) explain any or all connections between the heat system and the engine or where I could find this info and 2) point me in the direction I should be looking at, I would really appreciate it. I am almost certain its some kind of sensor or vacuum going awry.
Thanks!
I found this on turborx7.com but my car does this whether or not its cold or warm.
Hesitation at 3000 RPM when cold: No known cure.
I think it is caused by the double throttle control. Its purpose is to
prevent the engine from getting an overly lean fuel/air mix when you
first start to accelerate. Now the way this system works is that when
the engine is cold, (coolant below 175 degrees or so) the ECU opens the
double throttle control solenoid, which supplies vacuum to the double
throttle control actuator. This vacuum overcomes the spring tension
that normally holds the double throttle butterfly open, and it closes.
Now, think about what happens when you accelerate.... the engine pulls
less vacuum, and starts to go towards positive manifold pressure as you
build boost. With the vacuum going away, the plate returns to its
open (normal when engine warm) position. This helps explain why the car
doesn't hesitate when accelerating hard, and does when accelerating slowly.
The decision by the ECU to operate the double throttle control system is
affected by coolant temperature, and the current "map" that the ECU is
using. The Double Throttle control only happens during starting, cold
engine warm-up, and COLD engine with LIGHT LOAD operation. This map is
also affected by the 20k mile switch, which is why many people say that
the car never hesitated at 3000 RPM when it was new. The 20k mile switch
does the same thing that the EL switch does.... it adds base RPM to the
motor... which affects the ECU's decision as to what "map" it is currently
operating in.
This is just my personal theory, and may be wrong.
Last edited by RX7_GRL; Mar 26, 2008 at 10:58 AM.
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